1.更新apt包索引：
sudo apt update #这一步可能会报错, 参考遇到的问题2.通过HTTPS使用仓库(repository)安装：
sudo apt install apt-transport-https ca-certificates curl software-properties-common3.在/etc/apt/sources.list.d/docker.list文件中添加下面内容
echo 'deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable' >>/etc/apt/sources.list.d/docker.list
deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable4.添加Docker官方的GPG密钥：
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add --
5.安装
sudo apt install docker-ce
【报错】
E: Package 'docker-ce' has no installation candidate
E: Package 'docker-ce' has no installation candidate
【解决方法】
添加其他的源，更新库，再试：
sudo echo "deb https://download.docker.com/linux/ubuntu zesty edge" > /etc/apt/sources.list.d/docker.list
sudo apt update&&sudo apt install docker-ce
